Induction-motor



A. KIMBLE.

INDUCTION MOTOR.

APPLICATION man MAYIZI 1919.

1 ,375,461 Patented Apr. 19, 1921.

- UNITED5TATEs PATENT 0 wnns'a'o, WISCONSIN, ASSIGNOB rommraoiqqmg i-wnnsam-wisconsm, A CORPORATION or WIBCONSIN.1 I

INDUCTION-MOTOR.

Specification of Letters Patent. v Patented Apr, 19, 1921,

Application filed May 12, 1919. Serial No. 296,649.

Toallrwkomitma concern:

Be it known t at I, AUs'rrN KIMBLE, a citizen of the United States of America, and a resident. of Wausau, county of Marathon, and State ofjWisconsin, have invented certain. new. and useful Improvements in Induction-Motors, of which the following is a-specification. V j

This invention relates to squirrel cage structures for dynamo-electric machines, and to methods of forming same.

The main objects of the invention are to provide an improved form of conductor adapted to serve as a squirrel cage bar and capable of readily transmitting large currents of low frequency or of non-alternating character, but offering relatively high impedance to alternating currents of high frequency; and to provide-a squirrel cage rotor having improved ventilating means.

An illustrative embodiment of this invention is shown in the accompanying drawings, in which Figure 1 is a longitudinal section on the line 11 of Fi 2, of a squirrel cage rotor, one side bein iiroken away.'

Fig. 2 is su stantially an end view of the rotor with the shaft and the projecting ends of the squirrel ca e bars shown in section on the line 22 of %i 1.

In the construction shown in the drawings, the rotor comprises a laminated core 1 secured by threaded clamping rings 2 on the shaft 3. The squirrel cage carried by said core includes'a pair of end rings 1 and a peripheral series of bars 5 connecting'said rings. Each bar 5 consists of a core 6. of high reactance metal and a coating or sheath of low impedance metal, cast-iron rods being well adapted to serve as cores, and an electro-deposlt of copper being best adapted 'to serve as the covering 7. The said bars are disposed in slots 8 and are secured to the end rings in a substantially integral manner by any approved means, preferably brazing, as shown at 9.

The method of, forming and assembling the several parts is as follows: The bars for the squirrel cage are cut in suitable lengths from copper-plated stock, which may be supplied in any lengths which commercial convenience ma determine. The cores are assembled in t e usual manner as understood-in the art, andthe end rings 4 are applied thereto, after wh'ch thebars 5 are set into place and arrang d to project an equal distance at each end for ventilating purposes and are secured as above explained.

Although the compound bars 5 are not necessarily limited to the cylindrical sheath and core form shown, still the concentric distribution of the copper about the iron is considered best, as it is most favorable to the transmission of hi h frequency current. This form is also a vantageous' asbeing adapted for ready manufacture. v

Although the core openings for the bars 5. are designated as slots, it is to be understood that they may be of any approved form, including tubular perforations disposed adjacent to the core surface.

The operation of the machine is as follows: In starting the motor, the bars offer a relatively high egree of impedance, due to the high frequency of the current which tends to flow therein,'but as the machine comes up to speed, the frequency diminishes until, at or near synchronism, the current becomes substantially constant and unidirectional, so that the reactance becomes negligible and only the low ohmic resistance of the circuit has to be overcome.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing fromthe spirit of this invention as defined by thefollowing claims.

I claim: 1. A squirrel ca e winding comprising a air of low impe ance end rings, in comination with a peripheral series of compound bars connecting said rings, each bar including a core of high-reactance metal and a covering of low impedance metal.

2. A squirrel cage motor .device of the character described, comprising a laminated core with end rings thereon, and a series of compound connecting bars disposed in a peripheral series on said core, each bar including an inner core of high-reactance material and an outer covering of low impedance material. 1 igned at Chicago this 9th day of May,

AUSTIN KIMBLE. 

